Nuclear rocket puts Mars within reach

31 May 2013

Space travel to Mars and beyond may only be possible through the use of nuclear rocket technology, NASA suggests. Such spacecraft would be much faster than conventional craft, cutting the length of the mission and thereby reducing radiation exposure to astronauts.

A nuclear-powered craft could put man on Mars (Image: NASA)

NASA considers a 3% increased risk of fatal cancer as an acceptable career limit for its astronauts currently operating in low-Earth orbit. This translates to a cumulative dose of between 800 and 1200 milliSieverts (mSv).

Data from the radiation assessment detector of the Curiosity rover mission to Mars indicates that the rover was exposed to an average of 1.8 mSv of radiation per day on its 36-week journey to Mars. This suggests that astronauts travelling in conventional spacecraft would receive a dose of about 660 mSv during a round-trip to the planet, too close to NASA's current limit, making missions appear impracticable.

Cary Zeitlin, a principal scientist at the Southwest Research Institute, said, "In terms of accumulate dose, it's like getting a whole-body CT scan once every five or six days." He added, "Understanding the radiation environment inside a spacecraft carrying humans to Mars or other deep space destinations is critical for planning future crewed missions."

Nuclear option

One way to reduce the exposure of astronauts to radiation and other effects of space travel is to use faster spacecraft to cut the duration of their missions. A craft powered by a nuclear rocket engine could be the answer.

One approach uses a nuclear reactor to heat hydrogen to very high temperatures, which expands through a nozzle to generate thrust. NASA says that spacecraft powered by such engines generate higher thrust and are more than twice as efficient as conventional chemical rocket engines.

NASA said that the nuclear rocket engine would be designed to be safe throughout the mission and would not be started up until the craft had reached a safe orbit and was ready to begin its journey into deep space. Prior to startup, the nuclear system would be cold, with no fission products generated from nuclear operations, and with radiation below significant levels.

NASA has already reported the successful testing of power conversion and radiator systems for a nuclear power system it hopes to deploy on the Moon by 2020.

Russia is also working on a nuclear rocket that would generate electricity for a plasma thruster. The specific thrust of such a system could be 20 times that of current chemical rockets, cutting the time to travel to Mars to just over a month.

The Russian project to develop the nuclear thrust module began in 2010 with a budget of RUB17 billion ($532 million) and a plan to launch in 2018. The majority of this is allocated to Rosatom's development of the reactor unit, which should be ready for testing in 2017.